I have to say that I read the original post and felt a certain level of disgust.

What business is it of yours if a teacher someone pursues a student outside of the 'classroom'? I am friends with my sensei outside of training, and during class I'm fairly certain they extend a certain level of preferential treatment and attention to me; it's not necessarily fair, but it's human nature. Should he ignore someone he's got close to in 'real life', just because you have an irrational knee-jerk belief that there is something inherently wrong with an older man who is involved with a younger girl (by your own admission, nothing 'illegal' was taking place)?

And now they're in a happy, enduring relationship? How awful, sir. How truly awful. Lock up your daughter now, before she gets ensnared by someone who will stick by her for years.

Unless you have actual proof that something illegal transpired, I sincerely hope that you have kept these opinions to yourself; what you are implying (rather baselessly, from what you have said so far) can be extremely damaging to a person's reputation, career and personal relationships.

"Never escalate a battle unless forced to do so by your enemy" - Zordon